The present invention relates to remote targeting systems for guided missiles and more particularly to remote targeting systems for guided missiles wherein a means is provided for the missile seeker to lock-on a desired target signal while the missile is in flight and approaching the target. This situation occurs especially in tactical situations where long stand off by the launch aircraft is advisable. Various systems have been devised for guiding a missile to its target which have the disadvantages of requiring the aircraft to carry a separate transmitter pod for range gate synchronization or of a beam riding type that would require the launch aircraft to close toward the target and participate continuously in the attack, or of having an operator through a command link control the seeker target gates until the missile reached the target. All of these systems are complex and costly with respect to the equipment required in the missile. The present invention provides a target acquisition system which is particularly applicable to a situation in which the target has been detected and is being tracked by pulsed radar. The missile utilizes an inertial mid-course phase, and the seeker is an active radar type with range and azimuth tracking circuits which lock-on the desired target echo signal.
The target is detected by an airborne or shipboard radar operator who places cursors over the desired target signal as it appears on a plan position indicator radar display. The radar, a small computer in the aircraft or ship, and a transponder including a guidance transfer unit carried in the missile then combine to determine the bearing and range of the desired target with respect to the missile as it flies in the general direction of the target. This information, together with a detailed breakdown of the range signature of the target is automatically transmitted to the missile through a small phase modulation of the radar pulse repetition frequency. The phase modulated signal is received at the missile and decoded by the guidance transfer unit. The bearing portion of the target information is fed from the guidance transfer unit to the missile autopilot to correct the missile heading to coincide with the actual bearing to the target at the time of acquisition by the missile seeker. Similarly the computed missile-to-target range and detail range signature data are fed to the missile seeker. The range data are used to position the seeker antenna properly in pitch and to turn on the missile transmitter at the appropriate distance from the target. The seeker utilizes the range and detail signature data to obtain lock-on of its range tracker to the specific target desired.
Accordingly, an object of the present invention is to provide a system for locking a missile to a desired target signal while the missile is in flight.